Carry the surveyed room-in-roof block onto the SAP building part 🟩

_pashub_room_in_roof mirrors _api_build_room_in_roof: every surveyed RIR
surface (gable typed Exposed/Party per Table 4, slopes, common walls, flat
ceiling) becomes a detailed_surfaces entry of length x height, so the
cascade bills exact RIR surfaces instead of treating the shell as
well-insulated loft (issue #1590 bug 5).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

datatypes/epc/domain/mapper.py

@@ -154,6 +154,7 @@ from datatypes.epc.surveys.pashub_rdsap_site_notes import (
     HeatingAndHotWater,
     PasHubRdSapSiteNotes,
     Renewables as PasHubRenewables,
+    RoomInRoofSurfaceDetail,
     RoofSpaceDetail,
     Ventilation,
     WaterUse,
@@ -5979,6 +5980,64 @@ def _map_roof(
     return roof.insulation_at or None, thickness
 
 
+# PasHub gable "type" label → the Table 4 surface kind the cascade's
+# per-surface RR branch dispatches on (Exposed = as-common-wall U,
+# Party = 0.25 W/m²K).
+_PASHUB_GABLE_TYPE_TO_KIND: Dict[str, str] = {
+    "Exposed": "gable_wall_external",
+    "Party": "gable_wall",
+}
+
+
+def _pashub_room_in_roof(
+    roof: Union[RoofSpaceDetail, ExtensionRoofSpace],
+) -> Optional[SapRoomInRoof]:
+    """Build `SapRoomInRoof` from the surveyed §Roof-Space room-in-roof block
+    (RdSAP §3.10 detailed measurement), mirroring `_api_build_room_in_roof`:
+    every surveyed surface (gable / slope / common wall / flat ceiling)
+    becomes a `detailed_surfaces` entry of length × height, so the cascade
+    bills exact RIR surfaces instead of treating the whole shell as
+    well-insulated loft (issue #1590 bug 5). Returns None when no RIR is
+    lodged. A gable with an unmapped type label strict-raises."""
+    rir = roof.room_in_roof
+    if not roof.rooms_in_roof or rir is None:
+        return None
+    surfaces: List[SapRoomInRoofSurface] = []
+
+    def _add(
+        details: Optional[List[RoomInRoofSurfaceDetail]], kind: Optional[str]
+    ) -> None:
+        for d in details or []:
+            if d.length_m is None or d.height_m is None:
+                continue
+            surface_kind = kind
+            if surface_kind is None:  # gable — kind from the surveyed type
+                if d.gable_type not in _PASHUB_GABLE_TYPE_TO_KIND:
+                    raise UnmappedPasHubLabel(
+                        "room-in-roof gable type", str(d.gable_type)
+                    )
+                surface_kind = _PASHUB_GABLE_TYPE_TO_KIND[d.gable_type]
+            surfaces.append(
+                SapRoomInRoofSurface(
+                    kind=surface_kind,
+                    area_m2=d.length_m * d.height_m,
+                    u_value=d.u_value,
+                )
+            )
+
+    _add(rir.gables, None)
+    _add(rir.slopes, "slope")
+    _add(rir.common_walls, "common_wall")
+    _add(rir.flat_ceilings, "flat_ceiling")
+    if rir.floor_area_m2 is None:
+        return None
+    return SapRoomInRoof(
+        floor_area=rir.floor_area_m2,
+        construction_age_band=_extract_age_band(rir.age_range or ""),
+        detailed_surfaces=surfaces or None,
+    )
+
+
 def _map_main_building_part(
     construction: BuildingConstruction,
     measurements: BuildingMeasurements,
@@ -5989,6 +6048,7 @@ def _map_main_building_part(
     roof_location, roof_thickness = _map_roof(roof)
     return SapBuildingPart(
         identifier=BuildingPartIdentifier.MAIN,
+        sap_room_in_roof=_pashub_room_in_roof(roof),
         construction_age_band=_extract_age_band(main.age_range),
         # PasHub surveys never lodge a basement wall; pin the flag so a
         # "System Build" wall (code 6, which doubles as the gov-API basement